The present invention generally relates to additives for particulate materials, such as cementitious materials and non-cementitious materials. More specifically, the present invention relates to compositions that may improve the flow properties of dry particulate cementitious and non-cementitious materials and related methods of synthesis and use.
Cementitious materials such as hydraulic cements, slag, fumed silica, fly ash and the like having various particle size distributions are often dry-blended and placed in storage tanks. The storage tanks containing the cementitious materials are often transported by land or sea to locations where the cementitious materials are to be used. During such transportation, the cementitious materials are subjected to vibrations and as a result, under static conditions, the materials can become tightly packed. When the cementitious materials are conveyed out of the storage tanks, significant portions of the tightly packed materials may unintentionally be left behind in the storage tanks or clumps of the packed materials may become lodged in transfer conduits. Beyond the cost of the unusable cementitious materials, costly removal and disposal procedures may be required to remove the packed materials from the storage tanks or transfer conduits.
Treatments have been developed to reduce the likelihood that cementitious and non-cementitious materials will pack by improving or preserving the flow properties of the materials. Certain treatments involve blending dry particulate cementitious and/or noncementitious materials with an additive. One such additive comprises a particulate solid adsorbent material having a flow inducing chemical adsorbed thereon. In general, these additives are dry-blended with cementitious and/or non-cementitious materials at a point in time before packing is likely to occur, e.g., before the materials are shipped or stored. Typically, the dry-blending step occurs at a location other than the location where the cementitious or non-cementitious materials are ultimately utilized. For example, an additive may be dry-blended with cementitious materials in a warehouse before the blend is transported to a second location where it is used in a cementing operation.
While additives comprising a flow inducing chemical adsorbed onto a particulate solid adsorbent material may improve the flow properties of cementitious and noncementitious materials, certain undesirable properties of the additives may complicate or limit their use. In particular, known additives may conglomerate and/or freeze at relatively high temperatures. For example, the additives may begin to conglomerate at temperatures as high as 60° F. In other cases, additives may freeze at temperatures as high as 55° F. When completely frozen, an additive may lose its free-flowing, powder-like consistency and take the form of a solid, rock-like mass. This may be a tremendous disadvantage, because until the temperature of the additive can be raised, it may be difficult or impossible to dry-blend the additive with cementitious or non-cementitious materials. Typically, an additives' low freezing point may be most problematic prior to the point when the additive is dry-blended with an other material, e.g. when the additive is still in a relatively pure form. Due to the low freezing point of some additives, in cold climates the additives may have to be produced and/or stored in climate-controlled facilities, e.g., climate-controlled warehouses. If climate-controlled facilities are not available or are not cost effective, the additives may freeze and become at least temporarily unusable, because they cannot be dry-blended with cementitious or non-cementitious materials in a frozen state. In some cases, the freezing points of the individual components of the additive may be even higher than the freezing point of the finished additive, e.g., certain components may have freezing points above 60° F., so the components may freeze while the additive is being manufactured, making it difficult or impossible to produce the finished additive.